Terpenylalkylphenols and their preparation



Patented July 28, 1953 TEKPENYLALKYLPHENOLS AND THEIR PREPARATION LelandJ. Kitchen, Akron, Ohio, assignor to The Firestone Tire & RubberCompany, Akron, Ohio, a corporation of Ohio No Drawing. Application July12, 1950, Serial No. 173,489

4 Claims.

This invention relates to the terpenylalkylphenols and their production.This application is a continuation-in-part of my application Serial No.653,426 filed ,March 9, 1946, and now Patent No. 2,537,636.

Terpenylalkylphenols are advantageously prepared by alkylation ofterpenylphenols. The terpenylp-henols are usually prepared byterpenylation of a phenol (which may be an alkylated phenol) with aterpene hydrocarbon in the presence of an acid catalyst, such as astrong acid, ferric chloride and like salts, siliceous earths, halogens,etc. The usual reaction products contain terpenyl ethers of phenols andterpene polymerization products admixed with the nuclearly terpenylatedphenols. Substantially pure terpenylalkylphenols are preferred asnondiscoloring stabilizers for natural and synthetic rubbers as well asfor other uses. The invention includes the2,4-dialkyl-6-terpenylphenols, which are new compositions of matter, andmethods of obtaining them substantially free from side reactionproducts.

In general, steric hindrance prevents the inclusion of a terpenyl groupand two large alkyl groups in the same 2,4dialkyl-G-terpenylphenol. Thecommercial compounds of this type will, therefore, probably be limitedto those compounds with alkyl substituents containing no more than livecarbon atoms, and these are the preferred compounds of this invention.The preferred compounds of this type are the 2,4- dialkyl-6-isobornyl-,and fenchyl-phenols. According to the process of this invention, the2,4- dialkyl-G-terpenylphenols are obtained by condensation of a2,4-dialkylphenol with a suitable terpene hydrocarbon in the presence ofan acidic catalyst while heating at a temperature of about 70 to 130 0.,preferably with subsequent extraction of the reacted mixture with analkali metal base to remove unreacted phenol.

Most of the 2,4-dialkylphenolsused in prepar ing the compounds of thisinvention are soluble in water solutions of alkali metal bases. The 2,4-dialkyl-S-terpenylphenols' are insoluble or relatively insoluble inthese reagents. Treatment with an alkali metal hydroxide solution,therefore, affords a valuable method of separating from the desireddialkylterpenylphenol any excess or unreacted 2,4-dialkylphenol used inits preparation.

The 2A-dialkylphenols used as starting materials include those in whichthe alkyl groups are any of the following or a combination of any of thefollowing: methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl,isobutyl, tert-butyl or any of the various amyl groups. In general,larger alkyl groups are excluded from the invention, particularly thosein. the ortho position, because through steric hindrance there is atendency of generally preferred for use as catalysts.

the larger alkyl groups to prevent reaction of the nuclear carbons ofthe phenols with the terpene groups. The ZA-dimethylphenol is preferredfor carrying out the reaction not only because it reduces sterichindrance to a minimum but also because it is more readily soluble inalkali metal hydroxides than some of the other starting materialsindicated above.

In the case of a terpene wherein there are double bonds in conjugation,or a monocyclic terpene capable of isomerizing to a conjugated terpene,it is possible for the yield of 2,4-dialkyl-- G-terpenylphenol to bereduced. by chroman formation. Therefore stably bicyclic terpenes andtricyclic terpenes are preferred over the acylic terpenes and them'onocyclic terpenes.

The terpenes preferred for commercial operations because of theiravailability are camphene and tricyclene. Other bicyclic terpenes whichmay be used include the fenchenes, and bornylene. Tricyclic terpenesforinstance, tricyclene and cyclofenchene-may be used as terpene startingmaterials even though they contain no unsaturated linkages.

The acidic catalysts which may be used in carrying out the processinclude, for example, such well-known catalysts as sulfuric acid,phosphoric acid, benzenesulfonic acid, p-toluenesulfonic acid, stannicchloride, zinc chloride, aluminum chloride, fiuoboric acid, hydrofluoricacid, ferric chloride, and the boron trihalides, such as borontrichloride, boron trifluoride, and their ether complexes. A few percent by the weight of the catalyst is usually sufficient to give thedesired reaction.

Boron trifluoride and benzenesulfonic acid are Sulfuric acid tends tocause undesirable side reactions, such as sulfonation, oxidation, andpolymerization particularly at higher temperatures so that when thiscatalyst is used, a temperature not higher than C. will ordinarily bepreferred to minimize the side reactions. Boron trifiuoride-ethercomplex in the higher temperature range-for example, from to C.isusually considered objectionable in catalytic reactions and shouldusually be avoided in the production of the compounds of this inventionbecause of its tendency to be removed from the reaction mixture anddeposited on the walls of the condenser.

At temperatures above 130 C. there is a tendency for the terpenes toundergo undesirable side reactions, such as isomerization andpolymerization. Therefore, in carrying out the condensation, atemperature of about 70 to about 130 C. will be employed.

In carrying out the reaction, equimolecular proportions of thedialkylphenol and terpene 6'0- hydrocarbon may be used although theratio may the reaction mixture by a base, such as an alkali metalhydroxide.

It frequently is desirable to have a diluent present during the reactionin order to facilitate agitation during the condensation reaction and toaid in the working up of the reaction mixture by lowering its viscosity,since the 2,4-dialkyl-6- terpenylphenols are highly viscous liquids whenin the liquid state. Diluents which may be used satisfactorily includebenzene, toluene, ethylene chloride, and cyclohexane.

The 2,4-dialkyl-6-terpenylphenols usually are obtained as highly viscousliquids having a refractive index of about 1.52-1.54 (12 and a boilingpoint of at least 190 C. at a pressure of 10 millimeters of mercury.

EXAMPLE 1 2,4-dimethyl-6-isobornylphenol Equimolecular amounts ofcamphene and 2,4- dimethylphenol (272 grams of camphene and 244 grams of2,4-dimethylphenol) were dissolved in 300 milliliters of diluenttoluene; and 8 grams of catalyst, 70 per cent benzenesulfonic acid, wereadded. The mixture was heated at 129- 130 C. for nine and one-halfhours, then partially cooled, shaken once with about 500 milliliters of10 per cent NaOH solution, and distilled, using a Raschig-ring packedcolumn with an efiiciency of about five theoretical plates. Toluene wasdistilled from the reacted mixture at atmospheric pressure; and campheneand dimethylphenol were then distilled at 17 millimeters, then 10millimeters. The recovered camphene and dimethylphenol along with thedimethylphenol obtained by acidification of the caustic washingsamounted to 55 per cent of the weight of the starting reactants.

After collecting an ll-gram fore-run, 174 grams of2,4-dimethyl-6-isobornylpheno1 were obtained as a highly viscous liquidwith a light yellow tinge, boiling in the range l84195 C. at 10millimeters; it had n =1.5396. Seven grams of residue remained in thestill-pot.

The 2,4-dimethyl-G-isobornylphenol fraction soon crystallized onstanding at room temperature. After recrystallization from petroleumether, the soft furry crystals had a melting point of 81.6 to 819 C.

The total yield of 2,4-dimethyl-6-isobornylphenol was 35 per cent oftheory, based upon the total starting materials, or 89 per cent basedupon unrecovered starting materials.

EXAMPLE 2 2,4-dimethyZ-6-isobomylphenol One hundred grams of2,4-dimethylphenol containing 5 grams of concentrated sulfuric acid ascatalyst were heated at 70-80 C. with stirring for ninety minutes;during the first thirty minutes, 125 grams of camphene were added insmall amounts. The reaction mixture was washed, first with water, thenwith potassium carbonate solution. The oil layer was dried overanhydrous K2003, then distilled. After 56 grams of camphene fraction and61 grams of 2,4-dimethylphenol fraction had been distilled, 64 grams ofcrude 2,4-dimethyl-6-is0bornylphenol were obtained as a light yellowviscous liquid distilling in the range 105-163 C. at about 2millimeters; the main portion distilled at 142-147" C. The product had n=1.5366; the yield was 4 30 per cent of the theoretical. Thirteen gramsof residue remained in the still-pot.

EXAMPLE 3 2,4-di-sec-butyl-6-isobornylphenol A mixture of 206 grams of2,4-di-sec-buty1- phenol, 150 grams of camphene (10 per cent excess),and 7 grams of catalyst (boron trifluoride-ether complex) in 150milliliters of toluene diluent was heated at -125 C. for 7 hours.Another milliliters of toluene were added to the viscous dark brownreaction mixture to facilitate handling, and the mixture was washedtwice with 10 percent NaOH solution. It then was distilled through acolumn having an efficiency of about five theoretical plates. Afterdistillation of the solvent and 118 grams of lowboiling materialcontaining about 74 grams of unreacted 2,4-di-sec-butylphenol (boilingpoint 144/10 millimeters), there was obtained 196 grams (58 per centyield) of product, 2,4-di-secbutyl-6-isobornylpheno1, a highly viscousyellow liquid which was collected at -205 C./3 millimeters, and whichhad the refractive index n =1.5l95. Forty grams of solid resin remainedin the still-pot.

CHaCHzCHOHa CH CH:

1. 2,4-dialkyl6-isobornylphenols.

2. 2,4-dimethyl-6-isobornylphenol.

3. 2,4-dibutyl-6-isobornylphenol.

4. 2,4-di-sec-butyl-6-isobornylphenol.

LELAND J. KITCHEN.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,469,709 Wuyts Oct. 2, 1923 2,123,898 Honel et al. July 19,1938 2,145,369 Osterhof Jan. 31, 1939 2,186,132 Zink Jan. 9, 19402,343,845 Powers Mar. 7, 1944 2,471,454 Rummelsburg May 31, 19492,537,636 Kitchen Jan. 9, 1951 2,537,647 Kitchen Jan. 9, 1951 FOREIGNPATENTS Number Country Date 204,754 Great Britain Oct. 1, 1923 396,106Germany May 30, 1924 598,298 Germany June 8, 1934 OTHER REFERENCESMartin: Paint Manufacture, vol. 15, No. 2, pages 30-32, Feb. 1945.

Kitchen: Jour. Am. Chem. Soc, vol. 70, pages 3608-10, 1948.

